Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Canon ELPH 150 IS and Panasonic G3 side-by-side from the front, back and top in their relative dimensions. Canon ELPH 150 IS has external dimensions of 95 x 57 x 24 mm (3.74 x 2.24 x 0.94″) and weighs 142 g (0.31 lb / 5.01 oz) (including batteries). Panasonic G3 has external dimensions of 115 x 84 x 47 mm (4.53 x 3.31 x 1.85″) and weighs 336 g (0.74 lb / 11.85 oz) (including batteries).
Below you can see the front view size comparison of Canon ELPH 150 IS and Panasonic G3. Canon ELPH 150 IS is clearly the smaller of the two cameras. Its body is 20mm narrower, 27mm shorter and 23mm thinner than Panasonic G3. As you can tell, actually this is not a fair size comparison since Canon ELPH 150 IS has a built-in lens but Panasonic G3 doesn't. Once you put a lens on G3, its thickness will increase significantly.
Here is the back view size comparison of Canon ELPH 150 IS and Panasonic G3.
Now lets look at the top view comparison of Canon ELPH 150 IS and Panasonic G3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon ELPH 150 IS is significantly lighter (194g ) than the Panasonic G3 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on G3, the total kit will weigh much higher.
Unfortunately neither Canon PowerShot ELPH 150 IS (IXUS 155) nor Panasonic Lumix DMC-G3 provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Compact Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic G3's 3.00" LCD screen is slightly larger than Canon ELPH 150 IS's 2.7" screen.
Moreover, Panasonic G3 sports a Fully Articulated screen
which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over the head levels, and especially very useful for shooting selfies and video. On the other hand, Canon ELPH 150 IS has a fixed type screen which provides almost no flexibility in shooting positions compared to G3.